Small radio base stations installable in a user' house, office, or the like have been developed (see Patent Literatures 1 and 2, for example). Such a small radio base station is installed in a house, a small office, or the like by a user who owns the small radio base station, and is connected to an upper-level device on the side of a core network via an IP (Internet Protocol) communication network, such as the Internet, by using ADSL (Asymmetric Digital Subscriber Line) or an optical fiber line.
Such a small radio base station is generally called a femto base station, a femtocell base station, or a home base station. The size (coverage area) of a cell formed by a small radio base station is typically about several meters to several tens of meters, which is extremely smaller than that of a macro cell of the related art. For this reason, a cell formed by a small radio base station is called a femtocell, a home cell, or the like. The 3GPP (Third Generation Partnership Project) defines such a small radio base station as Home Node B (HNB) and Home evolved Node B (HeNB), and is proceeding with standardization work. The term “HNB” refers to a small radio base station for UTRAN (UMTS (Universal Mobile Telecommunications System) Terrestrial Radio Access Network). The term “HeNB” refers to a small radio base station for LTE (Long Term Evolution)/E-UTRAN (Evolved UTRAN).